High speed uplink packet access HSUPA (High Speed Uplink Packet Access) is an optimization and evolvement of packet services from a mobile terminal to a wireless access network in an uplink direction. Using self-adaptation encoding, physical-layer hybrid retransmission, Node B-based (NodeB, that is, base station) fast scheduling, and 2-ms TTI (Transmission Time Interval, transmission time interval)-based short-frame transmission, the HSUPA improves the highest data transmission rate and cell throughput, and reduces delay.
HSUPA data transmission is categorized into two cases: 2-ms TTI and 10-ms TTI. In case of the 2-ms TTI, a UE (User Equipment, user equipment) has eight HARQ (Hybrid Automatic Repeat Request, hybrid automatic repeat request) processes; and in case of the 10-ms TTI, a UE has four HARQ processes.
When the UE needs to transmit uplink data, the UE determines the size of a data transport block within the TTI in the corresponding HARQ process according to the grant value from a network, and transmits a data block to the network. The UE meanwhile saves the transmitted data block in the buffer of the HARQ process and waits for ACK/NACK (Acknowlegdement/Non-Acknowlegdement, acknowledgement/non-acknowledgement) information from the network. If the UE receives the ACK information from the network on an E-HICH channel (E-DCH (Enhanced Dedicated Transport Channel, enhanced dedicated transport channel) HARQ Acknowledgement Indicator Channel, E-DCH HARQ acknowledgement indicator channel), it means that the network has successfully demodulates the data. At this time, the UE clears the data block in the corresponding HARQ process. If the UE receives the NACK information or receives no information in a specified time from the network on the E-HICH, it means that the network fails to demodulate the data. At this time, the UE needs to retransmit the data block in this HARQ process until retransmission attempts reach the maximum retransmission times.
As shown in FIG. 1, taking the 2-ms TTI as an example, within each TTI only one HARQ process transmits data, and the UE transmits uplink data, and transmits data al in HARQ process 1 within a first RTT (Route-Trip Time, round-trip-time), and saves data a1 in a buffer. After receiving the NACK message network on the E-HICH, the UE retransmits data a1 in HARQ process 1 within a next RTT, that is, the data a1 is retransmitted after a time period equal to an RTT. Data A1 in HARQ process 2 represents the successfully transmitted data. Therefore, new data A2 is transmitted in HARQ process 2 within a next RTT.
The inventor, during implementation of the present invention, finds that when the HSUPA uses the MIMO (multiple input multiple output, multiple input multiple output) technology in the uplink direction, the UE may transmit two data blocks concurrently within a TTI, that is, dual stream data transmission. In this case, the network may send signaling to notify the UE to switch from a dual stream transmission mode to a single stream transmission mode. Or the UE transmits only one data block within a TTI, that is, single stream data transmission. In this case, the network may send signaling to notify the UE to switch from a single stream transmission mode to a dual stream transmission mode.
Therefore, when the UE works in the MIMO mode and transmits uplink data in the dual stream transmission mode, the UE is incapable of processing the data buffered in the HARQ process of a stopped data stream if receiving from the network a command instructing switching from the dual stream transmission mode to the singe-flow transmission mode. Similarly, when the UE works in the MIMO mode and transmits uplink data in the single stream transmission mode, the UE is capable of processing the data buffered in the HARQ process of an original data stream if receiving a command instructing switching from the single stream transmission mode to the dual stream transmission mode.